Alteration of Oral and Perioral Soft Tissue in Mice following Incisor Tooth Extraction.

Oral and perioral soft tissues cooperate with other oral and pharyngeal organs to facilitate mastication and swallowing. It is essential for these tissues to maintain their morphology for efficient function. Recently, it was reported that the morphology of oral and perioral soft tissue can be altered by aging or orthodontic treatment. However, it remains unclear whether tooth loss can alter these tissues' morphology. This study examined whether tooth loss could alter lip morphology. First, an analysis of human anatomy suggested that tooth loss altered lip morphology. Next, a murine model of tooth loss was established by extracting an incisor; micro-computed tomography revealed that a new bone replaced the extraction socket. Body weight was significantly lower in the tooth loss (UH) group than in the non-extraction control (NH) group. The upper lip showed a greater degree of morphological variation in the UH group. Proteomic analysis and immunohistochemical staining of the upper lip illustrated that S100A8/9 expression was higher in the UH group, suggesting that tooth loss induced lip inflammation. Finally, soft-diet feeding improved lip deformity associated with tooth loss, but not inflammation. Therefore, soft-diet feeding is essential for preventing lip morphological changes after tooth loss.

Development and Regeneration of Muscle, Tendon, and Myotendinous Junctions in Striated Skeletal Muscle.

Owing to a rapid increase in aging population in recent years, the deterioration of motor function in older adults has become an important social problem, and several studies have aimed to investigate the mechanisms underlying muscle function decline. Furthermore, structural maintenance of the muscle-tendon-bone complexes in the muscle attachment sites is important for motor function, particularly for joints; however, the development and regeneration of these complexes have not been studied thoroughly and require further elucidation. Recent studies have provided insights into the roles of mesenchymal progenitors in the development and regeneration of muscles and myotendinous junctions. In particular, studies on muscles and myotendinous junctions have-through the use of the recently developed scRNA-seq-reported the presence of syncytia, thereby suggesting that fibroblasts may be transformed into myoblasts in a BMP-dependent manner. In addition, the high mobility group box 1-a DNA-binding protein found in nuclei-is reportedly involved in muscle regeneration. Furthermore, studies have identified several factors required for the formation of locomotor apparatuses, e.g., tenomodulin (Tnmd) and mohawk (Mkx), which are essential for tendon maturation.

Endothelial-specific depletion of TGF-ß signaling affects lymphatic function.

BACKGROUND: Transforming growth factor (TGF)-ß is a multifunctional cytokine involved in cell differentiation, cell proliferation, and tissue homeostasis. Although TGF-ß signaling is essential for maintaining blood vessel functions, little is known about the role of TGF-ß in lymphatic homeostasis. METHODS: To delineate the role of TGF-ß signaling in lymphatic vessels, TßRIIfl/fl mice were crossed with Prox1-CreERT2 mice to generate TßRIIfl/fl; Prox1-CreERT2 mice. The TßRII gene in the lymphatic endothelial cells (LECs) of the conditional knockout TßRIIiΔLEC mice was selectively deleted using tamoxifen. The effects of TßRII gene deletion on embryonic lymphangiogenesis, postnatal lymphatic structure and drainage function, tumor lymphangiogenesis, and lymphatic tumor metastasis were investigated. RESULTS: Deficiency of LEC-specific TGF-ß signaling in embryos, where lymphangiogenesis is active, caused dorsal edema with dilated lymphatic vessels at E13.5. Postnatal mice in which lymphatic vessels had already been formed displayed dilation and increased bifurcator of lymphatic vessels after tamoxifen administration. Similar dilation was also observed in tumor lymphatic vessels. The drainage of FITC-dextran, which was subcutaneously injected into the soles of the feet of the mice, was reduced in TßRIIiΔLEC mice. Furthermore, Lewis lung carcinoma cells constitutively expressing GFP (LLC-GFP) transplanted into the footpads of the mice showed reduced patellar lymph node metastasis. CONCLUSION: These data suggest that TGF-ß signaling in LECs maintains the structure of lymphatic vessels and lymphatic homeostasis, in addition to promoting tumor lymphatic metastasis. Therefore, suppression of TGF-ß signaling in LECs might be effective in inhibiting cancer metastasis.

Transforming growth factor-ß signaling enhancement by long-term exposure to hypoxia in a tumor microenvironment composed of Lewis lung carcinoma cells.

Transforming growth factor-ß (TGF-ß) is a potent growth inhibitor in normal epithelial cells. However, a number of malignant tumors produce excessive amounts of TGF-ß, which affects the tumor-associated microenvironment by furthering the progression of tumorigenicity. Although it is known that the tumor-associated microenvironment often becomes hypoxic, how hypoxia influences TGF-ß signaling in this microenvironment is unknown. We investigated whether TGF-ß signaling is influenced by long-term exposure to hypoxia in Lewis lung carcinoma (LLC) cells. When the cells were exposed to hypoxia for more than 10 days, their morphology was remarkably changed to a spindle shape, and TGF-ß-induced Smad2 phosphorylation was enhanced. Concomitantly, TGF-ß-induced transcriptional activity was augmented under hypoxia, although TGF-ß did not influence the activity of a hypoxia-responsive reporter. Consistently, hypoxia influenced the expression of several TGF-ß target genes. Interestingly, the expressions of TGF-ß type I receptor (TßRI), also termed activin receptor like kinase-5 (ALK5), and TGF-ß1 were increased under the hypoxic condition. When we monitored the hypoxia-inducible factor-1 (HIF-1) transcriptional activity by use of green fluorescent protein governed by the hypoxia-responsive element in LLC cells transplanted into mice, TGF-ß-induced Smad2 phosphorylation was upregulated in vivo. Our results demonstrate that long-term exposure to hypoxia might alter responsiveness to TGF-ß signaling and affected the malignancy of LLC cells.

Smad2/Smad3 in endothelium is indispensable for vascular stability via S1PR1 and N-cadherin expressions.

Transforming growth factor-ß (TGF-ß) is involved in vascular formation through activin receptor-like kinase (ALK)1 and ALK5. ALK5, which is expressed ubiquitously, phosphorylates Smad2 and Smad3, whereas endothelial cell (EC)-specific ALK1 activates Smad1 and Smad5. Because ALK5 kinase activity is required for ALK1 to transduce TGF-ß signaling via Smad1/5 in ECs, ALK5 knockout (KO) mice were not able to give us the precise mechanisms by which TGF-ß/ALK5/Smad2/3 signaling is implicated in angiogenesis. To delineate the role of Smad2/3 signaling in endothelium, the Smad2 gene in Smad3 KO mice was selectively deleted in ECs using Tie2-Cre transgenic mice, termed EC-specific Smad2/3 double KO (EC-Smad2/3KO) mice. EC-Smad2/3KO embryos revealed hemorrhage leading to embryonic lethality around E12.5. EC-Smad2/3KO embryos exhibited no abnormality of vasculogenesis and angiogenesis in both the yolk sac and the whole embryo, whereas vascular maturation was incomplete because of inadequate assembly of mural cells in the vasculature. Wide gaps between ECs and mural cells could be observed in the vasculature of EC-Smad2/3KO mice because of reduced expression of N-cadherin and sphingosine-1-phosphate receptor-1 (S1PR1) in ECs from those mice. These results indicated that Smad2/3 signaling in ECs is indispensable for maintenance of vascular integrity via the fine-tuning of N-cadherin, VE-cadherin, and S1PR1 expressions in the vasculature.